DC sputtering process for making smooth electrodes and thin film ferroelectric capacitors having improved memory retention

Abstract

A ferroelectric thin film capacitor has smooth electrodes permitting comparatively stronger polarization, less fatigue, and less imprint, as the ferroelectric capacitor ages. The smooth electrode surfaces are produced by DC reactive sputtering.

What is claimed is:  
     
       1. A method of sputter depositing an essentially smooth electrode for use in integrated circuit thin film ferroelectric memory devices, said method comprising the steps of: 
       placing an integrated circuit substrate into a vacuum chamber in a DC sputtering device;  
       introducing a carrier gas mixture composed of a noble gas and a reactive gas species into said vacuum chamber; wherein said reactive gas species is twenty-five percent or less of said carrier gas;  
       using a DC glow discharge to sputter a conductive thin film using a target metal material onto said substrate in the presence of said carrier gas mixture,  
       said target metal material being selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, blends thereof, and oxides thereof; and  
       completing said integrated circuit memory device to include said conductive thin film as a conductive element in said integrated circuit.  
     
     
       2. The method as set forth in  claim 1  wherein said noble gas is argon. 
     
     
       3. The method as set forth in  claim 1  wherein said reactive gas species is oxygen. 
     
     
       4. The method as set forth in  claim 1  wherein said reactive gas species is ozone. 
     
     
       5. The method as set forth in  claim 1  wherein said reactive gas species includes hydrogen and oxygen. 
     
     
       6. The method as set forth in  claim 1  including a step of maintaining said carrier gas mixture ranging from 9×10 −3  to 2×10 −2  Torr during said step of using said DC glow discharge. 
     
     
       7. The method as set forth in  claim 1  including a step of forming a adhesion layer underneath said conductive film. 
     
     
       8. The method as set forth in  claim 7  wherein said forming said adhesion layer comprising the steps of: 
       placing an integrated circuit substrate into a vacuum chamber in a DC sputtering device;  
       introducing a carrier gas mixture comprised of a noble gas and a reactive gas species into said vacuum chamber;  
       using a DC glow discharge to sputter an adhesion layer using a target metal selected from said group onto said substrate in the presence of said carrier gas mixture.  
     
     
       9. The method as set forth in  claim 8  wherein said noble gas is argon. 
     
     
       10. The method as set forth in  claim 8  wherein said reactive gas species is oxygen. 
     
     
       11. The method as set forth in  claim 8  wherein said reactive gas species is ozone. 
     
     
       12. The method as set forth in  claim 8  wherein said reactive gas species includes hydrogen and oxygen. 
     
     
       13. The method as set forth in  claim 8  wherein said reactive gas species has a partial pressure ranging from 1.5% to 50% of said carrier gas. 
     
     
       14. The method as set forth in  claim 8  including a step of maintaining said carrier gas mixture ranging from 9×10 −3  to 2×10 −2  Torr during said step of using said glow discharge. 
     
     
       15. The method as set forth in  claim 1  including a step of forming a barrier layer underneath said conductive film. 
     
     
       16. The method as set forth in  claim 15  wherein said forming said barrier layer comprising the steps of: 
       placing an integrated circuit substrate into a vacuum chamber in a DC sputtering device;  
       introducing a second carrier gas mixture comprised of a second noble gas and a second reactive gas species into said vacuum chamber;  
       using a second DC glow discharge to sputter a barrier layer using a target metal onto said substrate in the presence of said second carrier gas mixture,  
       said target metal being selected from the group consisting of titanium, titanium tungstate, tantalum, tantalum silicide, tungsten, tungsten silicide, molybdenum, molybdenum silicide, palladium, rhodium, iridium, and ruthenium.  
     
     
       17. The method as set forth in  claim 16  wherein said second noble gas is argon. 
     
     
       18. The method as set forth in  claim 16  wherein said second reactive gas species is nitrogen. 
     
     
       19. The method as set forth in  claim 16  wherein said second reactive gas species is N 2 O. 
     
     
       20. The method as set forth in  claim 16  wherein said second reactive gas species is oxygen. 
     
     
       21. The method as set forth in  claim 16  wherein said second reactive gas species is ozone. 
     
     
       22. The method as set forth in  claim 16  wherein said second reactive gas species is a mixture of hydrogen and oxygen. 
     
     
       23. The method as set forth in  claim 16  wherein said second reactive gas species being selected at least two from the group consisting of nitrogen, N 2 O, oxygen, ozone, and hydrogen. 
     
     
       24. The method as set forth in  claim 17  wherein said second reactive gas species is less than 70% of said second carrier gas. 
     
     
       25. The method as set forth in  claim 17  including a step of maintaining said second carrier gas mixture ranging from 9×10 −3  to 2×10 −2  Torr during said step of using said second glow discharge. 
     
     
       26. The method as set forth in  claim 1  including a step of forming a ferroelectric layer over said conductive film. 
     
     
       27. The method as set forth in  claim 26  wherein said ferroelectric layer is a layered superlattice material. 
     
     
       28. The method as set forth in  claim 26  wherein said step of forming said ferroelectric layer includes depositing a liquid precursor to form a film of said precursor on said integrated circuit substrate. 
     
     
       29. The method as set forth in  claim 28  wherein said step of depositing said liquid precursor is followed by a step of drying said precursor film at a temperature less than 400° C. to provide a dried precursor residue. 
     
     
       30. The method as set forth in  claim 29  wherein said step of drying baking said film of said precursor is followed by steps of 
       soft baking said dried precursor residue using RTP at an RTP temperature ranging from 525° C. to 675° C. for a period of time ranging from thirty seconds to five minutes to provide a soft baked precursor residue; and  
       annealing said soft baked precursor residue in a diffusion furnace under oxygen at an anneal temperature ranging from 450° C. to 650° C.  
     
     
       31. The method as set forth in  claim 26  including, after said step of forming said ferroelectric layer, the steps of: 
       introducing a third carrier gas mixture comprised of a third noble gas and a third reactive gas species into said vacuum chamber; and  
       using a third DC glow discharge to sputter a second conductive film using a target metal material selected from said group onto said substrate in the presence of said third carrier gas mixture.  
     
     
       32. The method as set forth in  claim 31  wherein said third noble gas is argon. 
     
     
       33. The method as set forth in  claim 31  wherein said third reactive gas species is oxygen. 
     
     
       34. The method as set forth in  claim 31  wherein said third reactive gas species is ozone. 
     
     
       35. The method as set forth in  claim 31  wherein said third reactive gas species is a mixture of hydrogen and oxygen. 
     
     
       36. The method as set forth in  claim 31  including a step of maintaining said third carrier gas mixture ranging from 9×10 −3  to 2×10 −2  Torr during said step of using said third glow discharge. 
     
     
       37. The method as set forth in  claim 31  including, after said step of forming said second conductive film, the steps of: 
       introducing a fourth carrier gas mixture comprised of a fourth noble gas and a fourth reactive gas species into said vacuum chamber;  
       using a fourth DC glow discharge to sputter a second adhesion layer from a target metal onto said substrate in the presence of said fourth carrier gas mixture,  
       said target metal being selected from the group consisting of titanium, tantalum, palladium, rhodium, iridium, and ruthenium.  
     
     
       38. The method as set forth in  claim 37  wherein said fourth noble gas is argon. 
     
     
       39. The method as set forth in  claim 37  wherein said fourth reactive gas species is oxygen. 
     
     
       40. The method as set forth in  claim 37  wherein said fourth reactive gas species is ozone. 
     
     
       41. The method as set forth in  claim 37  wherein said fourth reactive gas species is a mixture of hydrogen and oxygen. 
     
     
       42. The method as set forth in  claim 37  wherein said fourth reactive gas species ranges from twenty-five to fifty percent of said fourth carrier gas. 
     
     
       43. The method as set forth in  claim 37  including a step of maintaining said fourth carrier gas mixture ranging from 9×10 −3  to 2×10 −2  Torr during said step of using said fourth glow discharge. 
     
     
       44. An integrated circuit device produced according to the method of  claim 1 . 
     
     
       45. A method of making a ferroelectric capacitor with sputter deposition of essentially smooth electrodes for use in integrated circuit memory devices, said method comprising the steps of; 
       placing an integrated circuit substrate into a vacuum chamber in a DC sputtering device;  
       introducing a carrier gas mixture comprised of a noble gas and a reactive gas species into said vacuum chamber; wherein said reactive gas species is twenty-five percent or less of said carrier gas;  
       using a DC glow discharge to sputter a first conductive thin film using a first target metal material onto said substrate in the presence of said carrier gas mixture,  
       said first target metal material being selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, blends thereof, and oxides thereof,  
       coating said conductive film with a liquid precursor capable of yielding a layered superlattice material upon drying and rapid thermal processing of said liquid precursor:  
       drying said liquid precursor at a temperature of less than 400° C. to provide a dried precursor residue;  
       rapid thermal processing said dried precursor residue at an RTP temperature ranging from 525° C. to 675° C. for a period of time ranging from thirty seconds to five minutes to provide a smooth surface atop said dried precursor residue;  
       using a DC glow discharge to sputter a second conductive thin film using a second target metal material onto said substrate in the presence of said carrier gas mixture,  
       said second target metal material being selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, blends thereof, and oxides thereof;  
       annealing layers resulting from said above steps;  
       patterning layers resulting from said above steps to provide a ferroelectric capacitor; and thereafter  
       completing said integrated circuit memory device to include said first and second conductive thin films as conductive elements in said Integrated circuit.  
     
     
       46. The method as set forth in  claim 45  wherein said step of coating is performed by liquid source misted chemical deposition. 
     
     
       47. The method as set forth in  claim 45  wherein said step of coating said conductive film includes coating said conductive film with a sufficient amount of liquid precursor to yield a layered superlattice material having a thickness ranging from 300 Å to 2500 Å. 
     
     
       48. The method as set forth in  claim 45  wherein said step of coating said conductive film includes coating said conductive film with a sufficient amount of liquid precursor to yield a layered superlattice material having a thickness ranging from 300 Å to 1100 Å. 
     
     
       49. The method as set forth in  claim 45  wherein said step of coating said conductive film includes coating said conductive film with a sufficient amount of liquid precursor to yield a layered superlattice material having a thickness ranging from 400 Å to 1000 Å. 
     
     
       50. The method as set forth in  claim 45  wherein said step of coating said conductive film includes coating said conductive film with a sufficient amount of liquid precursor to yield a layered superlattice material having a thickness ranging from 500 Å to 800 Å. 
     
     
       51. The method as set forth in  claim 45  wherein said step of rapid thermal processing said dried precursor residue is preformed at an RTP temperature ranging from 625° C. to 650° C. 
     
     
       52. The method as set forth in  claim 45  wherein said step of rapid thermal processing said dried precursor residue is preformed at an RTP temperature of 650° C. 
     
     
       53. The method as in  claim 45  wherein said step of annealing precedes said step of patterning. 
     
     
       54. The method as in  claim 45  wherein said step of annealing follows said step of patterning. 
     
     
       55. The method as in  claim 45  wherein said step of annealing includes a furnace anneal step. 
     
     
       56. The method as in  claim 45  wherein said step of annealing comprises heating to a temperature higher than the temperature of said rapid thermal processing step. 
     
     
       57. The method as in  claim 45  wherein said step of annealing comprises a plurality of anneals at different temperatures. 
     
     
       58. The method as in  claim 57  wherein said plurality of anneals are performed before said step of sputtering a second conductive thin film. 
     
     
       59. The method as in  claim 57  wherein one of said anneals is performed before said step of sputtering said second conductive thin film and one of said anneals is performed after said step of sputtering said second conductive thin film. 
     
     
       60. The method of  claim 57  wherein said anneal steps include a lower temperature anneal at a temperature lower than the temperature of said rapid thermal processing step and a higher temperature anneal at a temperature higher than said rapid thermal processing step. 
     
     
       61. The method of  claim 60  wherein said lower temperature anneal is performed before said step of sputtering a second conductive thin film and said higher temperature anneal is performed after said step of sputtering said second conductive thin film. 
     
     
       62. The method as in  claim 26  wherein said step of forming a ferroelectric layer includes the steps of rapid thermal processing said ferroelectric layer, annealing said ferroelectric layer, and patterning said ferroelectric layer. 
     
     
       63. The method as in  claim 62  wherein said step of annealing precedes said step of patterning. 
     
     
       64. The method as in  claim 62  wherein said step of annealing follows said step of patterning. 
     
     
       65. The method as in  claim 62  wherein said step of annealing includes a furnace anneal step. 
     
     
       66. The method as in  claim 62  wherein said step of annealing comprises heating to a temperature higher than the temperature of said rapid thermal processing step. 
     
     
       67. The method as in  claim 62  wherein said step of annealing comprises a plurality of anneals at different temperatures. 
     
     
       68. The method as in  claim 67  and further including the step of forming a second conductive thin film over said ferroelectric layer, and wherein said plurality of anneals are performed before said step of forming a second conductive thin film. 
     
     
       69. The method as in  claim 67  and further including the step of forming a second conductive thin film over said ferroelectric layer, and wherein one of said plurality of anneals is performed before said step of forming said second conductive thin film and one of said plurality of anneals is performed after said step of forming said second conductive thin film. 
     
     
       70. The method of  claim 67  wherein said plurality of anneal steps include a lower temperature anneal at a temperature lower than the temperature of said rapid thermal processing step and a higher temperature anneal at a temperature higher than said rapid thermal processing step. 
     
     
       71. The method of  claim 70  and further including the step of forming a second conductive thin film over said ferroelectric layer, and wherein said lower temperature anneal is performed before said step of forming a second conductive thin film and said higher temperature anneal is performed after said step of forming said second conductive thin film.